The effect of flicker rate on measured visual field extent in very young children.

PURPOSE: To investigate the effect of flicker rate on measured visual field extent in toddlers. METHODS: A total of 270 full-term children (90 each at 11-, 17-, and 30-months of age) and 36 adults were tested binocularly with an LED static perimetry procedure using a black double-arc perimeter. Each subject was tested with one of three flicker rates: 0, 3, or 10 Hz. The median farthest location seen and an interpolated estimate of the location at which 50% of the subjects detected the peripheral stimulus were calculated for each age group for each flicker rate. RESULTS: For 11-, 17-, and 30-month-old subjects, but not adults, flickering stimuli produced a larger measured visual field extent than nonflickering stimuli. For the 10-Hz stimuli, measured visual field extent in children did not differ from that of adults. CONCLUSIONS: In infants and young children, binocular measured visual field extent is enhanced by peripheral stimulus flicker. Maturity of the measured visual field depends on the stimulus parameters used during testing.     

The effect of flicker rate on nasal and temporal measured visual field extent in infants.

PURPOSE: To explore the effect of peripheral stimulus flicker rate on measured visual field extent (MVFE) in young infants. METHODS: Three hundred sixty infants (180 each at 3.5 and 7 months of age) were tested monocularly with a light-emitting diode static perimetry procedure using a double-arc perimeter with arms at 45 degrees , 135 degrees , 225 degrees , and 315 degrees . Each subject was tested with one of six flicker conditions: no flicker, 1 Hz, 3 Hz, 10 Hz, 20 Hz, and 40 Hz. An interpolated estimate of the location at which 50% of subjects detected the peripheral stimulus (corrected for spontaneous eye movements) and the mean location of the farthest spot seen were calculated across subjects for each perimeter arm for each flicker condition for each age group. RESULTS: Nasally, MVFE was larger for 7-month-old than for 3.5-month-old infants. Across both ages, infants showed larger MVFE for 10-Hz stimuli than for nonflickering stimuli, but MVFE did not differ between any other flicker conditions. Temporally, response to flicker varied with age. For 3.5-month-old infants, MVFE was smaller for the no flicker condition than for the 3-Hz, 10-Hz, and 20-Hz conditions, but there were no other differences across flicker conditions. For 7-month-old infants, MVFE was larger for 3-Hz stimuli than for the no flicker, 1-Hz, 20-Hz, and 40-Hz conditions, but there were no other differences across flicker conditions. Additional analyses showed that the effect of flicker rate on the percentage of subjects looking at a peripheral stimulus at a single eccentricity (29 degrees ) was similar to the effect of stimulus flicker across eccentricities, as reflected in MVFE. CONCLUSIONS: Peripheral stimulus flicker can enhance the MVFE in 3.5- and 7-month-old infants. However, the effect depends on flicker rate and is consistent with previous data indicating that 10 Hz and perhaps 3 Hz are especially effective in enhancing MVFE in older infants and young children.     

The influence of stimulus size on measured visual field extent in infants.

PURPOSE: To compare measured visual field extent for a 6 degrees stimulus (typical size used in studies of infants) with a 1.5 degrees stimulus (similar to the largest size used in Goldmann perimetry) in young infants. METHODS: A total of 120 infants (60 each at 3.5 months and 7 months of age) and 24 adults were tested monocularly with a kinetic perimetry procedure using a black double-arc perimeter. Each subject was tested with either a 6 degrees or 1.5 degrees white sphere, which was mounted on a black wand and moved smoothly toward the intersection of the perimeter arms at 3.4 degrees /s. Visual field extent along each perimeter arm was defined as the median of 2 to 3 measurements of the position of the leading edge of the stimulus when the subject made an eye movement toward the stimulus. RESULTS: The 6 degrees stimulus produced larger measured visual field extent than the 1.5 degrees stimulus in 3.5-month olds (temporal field only) and in 7-month olds (nasal and temporal field), but not in adults. CONCLUSIONS: Using the testing conditions of the present study, increasing stimulus size beyond the largest used in a Goldmann perimeter (approximately 2 degrees) increases measured visual field extent in young infants, but not in adults. This may relate to differences in peripheral summation areas or to differences in attentional factors between infants and adults.     

Misdirected visual motion in the peripheral visual field.

An object moving against a textured background is accurately perceived when viewed foveally, but when viewed peripherally the object's perceived direction of motion may deviate from veridical by as much as 90 deg. The illusory direction is oblique to the orientation of the background contours, which may themselves be moving or stationary. In several experiments, we examined the boundary conditions for occurrence of the illusion and tested hypotheses concerning its basis. This illusion of perceived direction dramatizes differences in motion processing between the fovea and the periphery.     

Stimulus motion increases measured visual field extent in children 3.5 to 30 months of age.

PURPOSE: To examine the influence of stimulus motion on measured visual field extent of 3.5- to 30-month-old children and adults. METHODS: Each subject was tested with LED-hybrid and LED-kinetic perimetry procedures, using a black double-arc perimeter. Targets in both procedures were identical in size, color, luminance, contrast, and flicker rate. However, in the LED-hybrid procedure, peripheral targets were sequentially illuminated from more peripheral to more central locations, whereas in the LED-kinetic procedure, a peripheral target on a black wand was manually moved centrally along the perimeter arm. A subset of subjects was also tested with white sphere kinetic perimetry (WSKP). RESULTS: The LED-kinetic procedure produced larger measured visual field extent than the LED-hybrid procedure in 3.5-, 11-, 17-, and 30-month-olds, but not in 7-month-olds or adults. Data from subjects tested with WSKP indicated that both stimulus motion and discrepancies in scoring methods contributed to the difference reported previously between visual field measurements obtained with WSKP vs. LED-hybrid perimetry. CONCLUSION: In infants and toddlers, measured visual field extent is larger for moving than for nonmoving targets. Further research is needed to determine whether the effect of motion is related to the visual system or to attentional factors.     

SITA visual field testing in children.

PURPOSE: The Swedish Interactive Thresholding Algorithm (SITA) is a new testing strategy for the Humphrey perimeter. The standard SITA algorithm shortens test time in adults without increasing variability, but its usefulness for detecting field defects in children has not been investigated. METHODS: We evaluated 92 standard SITA 24-2 visual fields of children, most of whom had various types of optic neuropathies (pediatric idiopathic intracranial hypertension, homonymous defects, bitemporal defects, papilledema from brain tumors), and compared them with 49 full threshold 24-2 fields obtained in similar patients. We evaluated outcome measures of foveal threshold, mean defect, pattern standard deviation, false-negative and false-positive rates, and test time. Five children (9 eyes) had both SITA and full threshold testing (FTT). RESULTS: The SITA decreased test time by over 50% compared with FTT (12.6 +/- 3.0 minutes vs 6.6 +/- 1.6 minutes [P <.00001]). When patients with field defects were eliminated, the pattern standard deviation was lower with SITA than FTT (P <.002), indicating lower intratest variability of SITA in subjects with normal fields. No detectable difference was observed in the other outcome measures. Subjective analysis of gray-scale fields in patients who underwent testing with the use of both strategies showed marked similarities. CONCLUSIONS: SITA shortens test time significantly compared with FTT and does so without jeopardizing interpretability. SITA has less intratest variability than FTT and therefore should be better for detecting and following defects. Caution is advised when following a visual field defect unless the same strategy is used for each evaluation. Switching strategies in the absence of a stable field defect is not recommended.     

Rocket-ship psychophysics. Assessing visual functioning in young children

A set of psychophysical procedures is described for rapidly measuring visual functions such as spatial contrast sensitivity, flicker fusion, and rod and cone two-color increment thresholds in young children. The psychophysical procedures, disguised as electronic space games, use a forced-choice paradigm combined with the method of descending limits. Because children enjoy the tasks and are highly motivated, the tests yield good sensory thresholds in a short period of time. However, when thresholds from 6-8-year-old children are compared with those of adults, the children have slightly higher thresholds for all of the functions tested. The differences are ascribed to the tendency of children to adopt a guessing strategy when stimuli are close to threshold.     

Central visual field changes using flicker perimetry in type 2 diabetes mellitus

PURPOSE: To evaluate the efficacy of flicker perimetry compared with that of static perimetry in determining central visual field losses in participants with type 2 diabetes mellitus. METHODS: Flicker and static perimetry were performed using the Medmont field analyser on 20 participants with type 2 diabetes mellitus and 24 age-matched control participants. RESULTS: Flicker, but not static, perimetry demonstrated significant reductions in thresholds in those participants who had a recent diagnosis of diabetes or who had no or only minimal diabetic retinopathy compared to the control group at eccentricities close to fixation. CONCLUSION: Flicker perimetry is recommended for the evaluation of visual field losses in participants with recent onset of diabetes and minimal diabetic retinopathy.     

Temporal frequency filters in the human peripheral visual field.

The temporal filtering properties of the human peripheral field were investigated by means of measuring: (1) modulation transfer functions for a range of spatial frequencies at four visual field locations (0, 10, 30 and 50 degrees), (2) the contrast of a masking stimulus required to extinguish the visibility of just suprathreshold probes. Results suggest that the number of temporal filters governing detection threshold is dependent upon both eccentricity and spatial frequency. For near-foveal viewing three temporal filters were found (one low-pass and two band-pass), whereas at far eccentricities only one was found (band-pass). A similar result was obtained by modeling the modulation transfer function by simply scaling the sensitivities of three independently derived filters. Our data suggest that (1) changes in the modulation transfer function with respect to spatial frequency and eccentricity can be adequately explained by the changes in sensitivity of a small number of spatio-temporal separable filters; (2) the peripheral field is not merely a coarser version of the fovea but has qualitative differences which may be thought to emphasize the transient properties of the stimulus.     

Motion perception in the peripheral visual field

Thresholds were determined for the perception of the motion of a single bar moving at different positions in the field of view. Performance in the temporal hemified was slightly superior to that in the nasal hemifield and depended on the orientation as well as on the direction of the motion. The perception of horizontal motion was better than that of vertical motion. In spite of large variations, centrifugal motion was significantly more readily perceived than centripetal motion.Supported by DFG-grant Fa 119/5-1 (Heisenberg Programm)     

Binocular summation in the peripheral visual field

Purpose: To investigate binocular summation for a light detection task in the central and peripheral retina along 4 meridians. Methods: 10 young subjects aged 22-30 years (mean 26 years) with healthy eyes and normal visual fields participated in the study. A custom-designed program on a Humphrey Visual Field Analyser measured thresholds at the fovea and at 5°, 10°, 15°, 25°, 40° and 55° along the horizontal meridian, and at 5°, 10°, 15°, 25°, 40° along the vertical, 45° oblique and 135° oblique meridians. Right and left monocular fields and binocular fields were measured on each subject using white spot stimuli (Goldmann sizes I and III). Binocular summation ratios were calculated for each eccentricity by dividing binocular sensitivity be the better monocular sensitivity. Results and conclusion: As expected, binocular and monocular sensitivities decreased with increasing eccentricity. The mean binocular summation ratio at the fovea was 1.38 for size I stimulus and 1.42 for size III. Binocular summation was demonstrated in the peripheral retina along all meridians and is of similar magnitude to foveal binocular summation. ANOVA showed that binocular summation was significantly higher in the vertical meridian than horizontal meridian for both size I and III stimuli. There was no significant variation in binocular summation ratios with eccentricity along any of the 4 meridians examined.     

The development of visual acuity in very young kittens. A study with forced-choice preferential looking

The development of visual acuity was studied longitudinally in young kittens, using a modification of the forced-choice preferential looking method (FPL) devised by Teller et al. [Vision Res. 14, 1433-1439 (1974)] for human infants. Acuity, defined as the spatial frequency which yields 70% correct responses by a naive observer, shows a 16-fold increase between 2 and 10 weeks of age. At comparable ages, acuity evaluated by this method falls short of the acuity values obtained with the mumping stand or with electrophysiological methods. FPL acuity estimated with a more lenient criterion (58%) comes close to the resolution of the highest-resolving single cells in the striate cortex. These results suggest that the preferential looking procedure provides a method that can be used in kittens over a wide age range, including ages at which it is impossible to use the jumping stand method.     

正常人周边区与中央区视觉诱发电位的变化规律

目的探讨正常人周边区与中央区图形翻转视觉诱发电位(visualevokedpotential,VEP)的变化规律。方法以图形翻转VEP作为研究工具研究18例正常人30°以外的上方、下方、鼻侧、颞侧4个方向周边区与中央区在Oz导程对比的图形VEP的波形特征。结果正常人的周边VEP在这4个方向上的N75、P100的潜伏期均随空间频率的增大而增大;N75-P100的峰值却有一个最适的空间频率,即N75-P100峰值只在这个最适空间频率下最大;另外周边区VEPN75、P100的潜伏期均较中央区VEPN75、P100的潜伏期明显延长,周边区VEPN57-P100的峰值均较中央区VEPN75-P100的峰值低。结论视网膜不同区域在枕叶投射的部位决定VEP的潜伏期。     

Discrepancies between single stimulus and multiple stimulus visual field examinations with the Peritest semi-automated perimeter in glaucoma patients

In a total of 24 randomly selected eyes of glaucoma patients, tested with the automated (single stimulus) and the manual (multiple stimulus) modes of the semi-automated Peritest perimeter, the numbers and depths of defects were compared as estimated with these two different measurement strategies. It was found that with the manual technique considerably less defects were detected than with the automated strategy.     

Relationship between the extent of peripheral anterior synechiae and the severity of visual field defects in primary angle-closure glaucoma

We investigated the relationship between the circumferential extent of peripheral anterior synechiae (PAS) and the severity of visual field defects in primary angle-closure glaucoma (PACG). Correlations between visual field defects and the extent of PAS were analyzed in 73 eyes; 28 with and 45 without acute attacks. Spearman's correlation coefficient between the severity of visual field defects and the extent of PAS was 0.348 (P = 0.003) in all subjects (n = 73), 0.377 (P = 0.012) in the PACG eyes without acute attacks (n = 45), and 0.338 (P = 0.079) in the eyes with acute attacks (n = 28). Our results showed a statistically significant correlation between the extent of PAS and the severity of visual field damage in PACG overall, and especially in PACG patients without a history of acute attacks.     

正常人周边区与中央区图形翻转视觉诱发电位的对比研究

目的了解视觉系统正常人周边区与中央区图形翻转视觉诱发电位的变化规律。方法以图形翻转视觉诱发电位作为研究工具,观察正常人30°以外的上方、下方、鼻侧、颞侧四个方向周边区与中央区的PVEP的波形特征。结果正常人的周边VEP在这四个方向上的N_(75)、P_(100)的潜伏期均随空间频率的增大而增大;N_(75)-P_(100)的峰峰值却有一个最适的空间频率,即N_(75)-P_(100)的峰峰值只在这个最适空间频率下最大;另外周边区VEP N_(75)、P_(100)的潜伏期均较中央区VEP N_(75)、P_(100)的潜伏期明显延长,周边区VEP N_(75)-P_(100)的峰峰值均较中央区VEP N_(75)-P_(100)的峰峰值低。结论正常人周边区与中央区图形翻转视觉诱发电位的是两种不同机制。